fix dfs.namenode.get-blocks.check.operation's deecription and Unify the configuration of namenode and balancer for getblocks request

Author: xiezhineng

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/balancer/NameNodeConnector.java

@@ -147,11 +147,11 @@ public static void checkOtherInstanceRunning(boolean toCheck) {
 
   private final BalancerProtocols namenode;
   /**
-   * If set requestToStandby true, Balancer will getBlocks from
+   * If set getBlocksToStandby true, Balancer will getBlocks from
    * Standby NameNode only and it can reduce the performance impact of Active
    * NameNode, especially in a busy HA mode cluster.
    */
-  private boolean requestToStandby;
+  private boolean getBlocksToStandby;
   private String nsId;
   private Configuration config;
   private final KeyManager keyManager;
@@ -191,9 +191,9 @@ public NameNodeConnector(String name, URI nameNodeUri, Path idPath,
 
     this.namenode = NameNodeProxies.createProxy(conf, nameNodeUri,
         BalancerProtocols.class, fallbackToSimpleAuth).getProxy();
-    this.requestToStandby = conf.getBoolean(
-        DFSConfigKeys.DFS_HA_ALLOW_STALE_READ_KEY,
-        DFSConfigKeys.DFS_HA_ALLOW_STALE_READ_DEFAULT);
+    this.getBlocksToStandby = !conf.getBoolean(
+        DFSConfigKeys.DFS_NAMENODE_GETBLOCKS_CHECK_OPERATION_KEY,
+        DFSConfigKeys.DFS_NAMENODE_GETBLOCKS_CHECK_OPERATION_DEFAULT);
     this.config = conf;
 
     this.fs = (DistributedFileSystem)FileSystem.get(nameNodeUri, conf);
@@ -318,7 +318,7 @@ public DatanodeStorageReport[] getLiveDatanodeStorageReport()
   private ProxyPair getProxy() throws IOException {
     boolean isRequestStandby = false;
     ClientProtocol clientProtocol = null;
-    if (requestToStandby && nsId != null
+    if (getBlocksToStandby && nsId != null
         && HAUtil.isHAEnabled(config, nsId)) {
       List<ClientProtocol> namenodes =
           HAUtil.getProxiesForAllNameNodesInNameservice(config, nsId);

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -4123,8 +4123,8 @@
   <name>dfs.namenode.get-blocks.check.operation</name>
   <value>true</value>
   <description>
-    Whether enable checkOperation when call getBlocks.
-    It is enabled (true) by default.
+    Set false to disable checkOperation and getBlocks for Balancer
+    will route to Standby NameNode for HA mode setup.
   </description>
 </property>
 <property>